Bandage for autolytic wound debridement

ABSTRACT

A bandage for autolytic debridement includes a fluid-impermeable enclosure having a sidewall forming a margin defining an opening, and a skin-facing surface that surrounds the opening. An attachment means is disposed on the skin-facing to attach the enclosure to the skin, with the margin extending outside of and surrounding at least the bed of a wound. When the enclosure is attached to the skin it creates a closed, fluid-impermeable chamber over a wound, substantially without contacting the wound. The bandage includes a fluid absorbent material disposed in the fluid-impermeable enclosure at or near the continuous margin, and out of the opening. The fluid absorbent material is thus positioned to receive and retain exudated fluid that originates in the wound, thereby by promoting autolytic debridement. The closed, fluid-impermeable chamber maintains a near-100% humid atmosphere about the wound, thereby promoting healing of the wound. The humid atmosphere and the structure of the bandage tend to maintain the temperature of the atmosphere about the wound at or near a normothermic level in the range of about 36° C. to about 38° C., thereby maintaining physiologic processes that drive autolytic debridement and wound healing.

CROSS-REFERENCES TO RELATED PATENTS AND COPENDING PATENT APPLICATIONS

[0001] This application contains material related to the followingcommonly assigned pending U.S. Patent Applications:

[0002] Ser. No. 07/900,656, filed Jun. 19, 1992, for “THERMAL BODYTREATMENT APPARATUS AND METHOD”;

[0003] Ser. No. 08/342,741, filed Nov. 21, 1994, for WOUND TREATMENTDEVICE”;

[0004] Ser. No. 08/356,325, filed Feb. 21, 1995, for “WOUND COVERING”;

[0005] Ser. No. 08/785,794, filed Jan. 21, 1997, for “NORMOTHERMICHEATER WOUND COVERING”;

[0006] Ser. No. 08/786,713, filed Jan. 21, 1997, for “NORMOTHERMICTISSUE HEATING WOUND COVERING”;

[0007] Ser. No. 08/786,714, filed Jan. 21, 1997, for “NEAR HYPOTHERIMICHEATER WOUND COVERING”;

[0008] Ser. No. 08/838,618, filed Apr. 11, 1997, for “FLEXIBLENON-CONTACT WOUND TREATMENT DEVICE”;

[0009] Ser. No. 08/843,072 filed on Apr. 11, 1997 entitled “FLEXIBLENON-CONTACT WOUND TREATMENT DEVICE WITH A SINGLE JOINT”;

[0010] Ser. No. ______ filed ______ for “WOUND TREATMENT APPARATUS WITHHEAT SPREADING DEVICE”;

[0011] Ser. No. ______ filed ______ for “WOUND TREATMENT APPARATUS WITHINFRARED ABSORPTIVE WOUND COVER”;

[0012] Ser. No. ______ filed ______ for “WOUND TREATMENT APPARATUS WITHA HEATER ADHESIVELY JOINED TO A BANDAGE”; and

[0013] Ser. No. ______ filed ______ for “WOUND TREATMENT APPARATUS FORNORMOTHERMIC TREATMENT OF WOUNDS”.

BACKGROUND OF THE INVENTION

[0014] The invention concerns the removal of dead tissue from a wound,and more particularly, a bandage that promotes the removal of deadtissue by substances that the body itself produces.

[0015] Chronic wounds are a common aliment, afflicting over 5 millionpeople annually in this country. The majority of chronic wounds arecaused by a local or generalized vascular insufficiency that reducesblood flow to the skin and subcutaneous tissue. The most common type ofchronic wounds include: pressure ulcers (decubiti, or “bed sores”);diabetic ulcers; arterial ulcers; venous ulcers; or a combination ofthese. Chronic wounds are full-thickness skin injuries that may be verylarge and that may persist for months or years.

[0016] The treatment of chronic wounds presents may challenges. First,chronic wounds frequently exude large volumes of fluid. In the case ofvenous leg ulcers or pressure ulcers, this fluid may primarily be aserous transudate consisting of plasma and interstitial fluid. In thecase of an infected or heavily colonized wound or a wound with necrotic(dead) tissue, the fluid will contain many white blood cells, cellulardebris, and toxic cellular metabolic waste products. Such fluid iscommonly denominated as “exudate” or “pus”.

[0017] Historically, the philosophy of wound management has encourageddrying a wound. To promote drying, a wound would be covered with asimple absorbent gauze, or left open to the air to dry. At times, heatmay have been applied to the wound to enhance drying. It is nowrecognized that drying the wound can actually inhibit healing.

[0018] Currently, the goal of wound management is to keep a wound moist.This may be accomplished by trapping exudate or transudate in a woundbed under a substantially fluid-impermeable bandage. This practiceavoids drying a wound, but leads to a new problem. In this regard,larger amounts of fluid from moderate or heavily exudating wounds mayresult in a pool of trapped fluid under the bandage. This pool of fluidis in constant contact with the wound and the peri-wound skin, which isa margin of skin that surrounds and abuts the wound. As a result, thewound and peri-wound tissues are constantly wet, which can lead tomaceration and further damage. Additionally, the fluid contains cellulardebris and metabolic waste products that may be toxic to the livingtissue of the wound bed and peri-wound. The toxicity of the fluid mayretard wound healing and, indeed, may damage healthy peri-wound tissueand already healed wound tissue.

[0019] Consequently, there is a need for a device that maintains anenvironment of high humidity over a wound in order to preventevaporative drying of the wound while, at the same time, managing theexcess fluid to keep it away from the peri-wound skin and the wound bed.In short, there is a need for a device that will keep a wound areahumid, but not wet.

[0020] One significant advantage to be gained by use of such a devicewould be optimization of autolytic debridement. Autolytic debridementdenotes the body's natural ability to break down dead tissue, therebycontinuously cleaning a wound so that new skin cells can grow to filland cover the wound, thereby promoting its healing. In this regard,“autolytic” refers to the destruction of dead tissue by agents producedby the body. “Debridement” is the removal of dead cells or tissue from awound. Autolytic debridement is therefore the breaking down and removalof dead tissue from a wound by substances and processes that are naturalto the body. This function is carried out by white blood cells generallyknown as phagocytes, and by a variety of enzymes. In the process thephagocytes die and add to the cellular debris of the necrotic tissue inthe exudate fluid. The exudate fluid flows away from the wound, therebyremoving the dead cells and other debris. Autolytic debridement underprior art wound bandages is usually ineffective at cleaning woundsbecause the exudate fluid collects and pools in the wound. Cliniciansmust frequently intervene by resorting to repeated surgical debridementin order to clean necrotic tissue from a wound. There is a needtherefore to support and enhance autolytic debridement by removingexudate with its toxic waste by-products from the wound area.

[0021] Since autolytic debridement is an autogenic process, driven bythe functioning of body systems, it is affected by temperature. In thisregard, hypothermia is known to slow or even stop cellular functions,immune system functions, enzyme reactions, and biochemical processes.Effective phagocytosis requires an active immune system, active cellularfunctions, and rapid enzyme and biochemical reactions. Many wounds,because of their locations on body limbs, are hypothermic. The coolenvironment of these wounds slows down the process of autolyticdebridement, extending the time required for healing.

[0022] Accordingly, the need for a device to keep a wound area humid,but not wet, is compounded by the need for the device to enhanceautolytic debridement by carrying exudate away from the wound andkeeping the wound warm.

BRIEF SUMMARY OF THE INVENTION

[0023] We have invented a device that meets these needs by maintaining awarm, humid environment at and over a wound and by collecting exudatefluid at a location away from the wound and peri-wound area, therebyenabling the process of autolytic debridement.

[0024] Our invention embraces at least two components. First is anon-contact bandage with an outer shell that creates an enclosure overand about a wound, that does not touch the wound. The enclosure includesan adhesive attachment means that adhesively attaches the bandage to theskin around the wound, forming a chamber that is substantially sealedover the wound. Second, a fluid absorbent material is placed inside thechamber, away from the wound to absorb fluid from the wound.

[0025] More particularly, the invention is a bandage for autolyticdebridement that includes a fluid-impermeable enclosure having asidewall forming a margin that defines an opening, and a skin-facingsurface extending beyond the margin away from the opening. An attachmentmeans is disposed on the skin-facing surface for attaching the enclosureto skin to create a closed, fluid-impermeable chamber over a wound,substantially without contacting the wound. A fluid absorbent materialis disposed in the fluid-impermeable enclosure substantially at or nearthe margin and out of the opening.

[0026] Significant advantages are realized when our bandage forautolytic debridement is used. In forming a closed, fluid-impermeablechamber over a wound, our bandage maintains an environment of almost100% relative humidity over the wound, thereby preventing evaporativedrying of the wound. The enclosure and its humid atmosphere tend toretain warmth or heat, thereby raising the temperature of the tissues inthe peri-wound area and the wound bed to a near-normothermic level, thatis a level in the range of about 36° C. to about 38° C. Dispellinghypothermia in these tissues enhances the physiologic processes thatdrive autolytic debridement. The collection of exudate fluid at alocation away from the wound bed reduces or eliminates pooling on thewound bed and peri-wound area, which tends to accelerate autolyticdebridement and promote wound healing. Finally, since the bandage doesnot touch the wound, its removal does not tear away growing cells at themargin and in the bed of a wound. Lifting or removal of our bandage willnot cause bleeding in the wound or morbid damage to growing cells.

[0027] These advantages and other profitable characteristics of ourbandage will become apparent when the following detailed description isread with reference to the below-described drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0028]FIG. 1 is an isometric drawing of a first embodiment of a bandagefor autolytic debridement.

[0029]FIG. 1A is an isometric section taken along A-A in FIG. 1.

[0030]FIG. 1B is an enlarged partial side sectional view of a portion ofthe isometric section shown in FIG. 1A.

[0031]FIG. 2 is an isometric drawing of a second embodiment of a bandagefor autolytic debridement.

[0032]FIG. 2A is an isometric section taken along A-A of FIG. 2.

[0033]FIG. 2B is a partial side sectional view showing details of theisometric section of FIG. 2A.

[0034]FIGS. 2C and 2D are side sectional views showing variations in thestructure and elements of the second embodiment.

[0035]FIG. 3 is an isometric section view of a third embodiment of abandage for autolytic debridement.

[0036]FIG. 3A is a side sectional view taken along A-A of FIG. 3.

[0037]FIG. 4 is an isometric drawing of a fourth embodiment of a bandagefor autolytic debridement.

[0038]FIG. 4A is a side sectional view taken along A-A of FIG. 4.

[0039]FIG. 5 is an isometric drawing of a fifth embodiment of a bandagefor autolytic debridement.

[0040]FIG. 5A is a side sectional view taken along A-A of FIG. 5.

[0041]FIG. 6 is an isometric drawing of a sixth embodiment of a bandagefor autolytic debridement.

[0042]FIG. 6A is a side sectional view taken along A-A of FIG. 6.

[0043]FIG. 7 is an isometric section illustrating a seventh embodimentof a bandage for autolytic debridement.

[0044]FIG. 7A is a side sectional view taken along A-A of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

[0045] Our invention is a bandage for autolytic debridement. The bandageincludes a fluid-impermeable enclosure having a sidewall that forms amargin defining an opening, and a skin-facing surface surrounding theopening. An attachment means is disposed on the skin-facing surface toattach the enclosure to the skin, with the margin extending outside ofand surrounding at least the bed of a wound, if not an annulus ofperi-wound tissue around the wound. When the enclosure is attached tothe skin it creates a closed, fluid-impermeable chamber over a wound,substantially without contacting the wound. The bandage includes a fluidabsorbent material disposed in the fluid-impermeable enclosure, at ornear the continuous margin, and out of the opening. The fluid absorbentmaterial is thus positioned to receive and retain exuded fluid thatoriginates in the wound. The closed, fluid-impermeable chamber maintainsa near-100% humid atmosphere about the wound. The humid atmosphere andthe structure of the bandage tend to maintain the temperature of theatmosphere about the wound at or near a normothermic level in the rangeof about 36° C. to about 38° C.

[0046] Reference now to the figures will provide an understanding ofvarious embodiments of our bandage for autolytic debridement. Although aplurality of embodiments are shown, it will be manifest that eachembodiment includes at least the above-described elements andlimitations of our bandage for autolytic debridement.

[0047] Referring now to FIGS. 1, 1A and 1B, a first embodiment of abandage for autolytic debridement according to our invention isillustrated. The bandage 10 includes an enclosure 12 having the shape ofan inverted saucer with a depression 14 defined by a sidewall 16 thathas the shape of an annulus, preferably a continuous annulus. Thesidewall 16 transitions to a compressed ring 18. The lower insidesurface of the sidewall 16 defines an inner margin 20, while the outsideedge of the compressed ring 18 defines an outer margin 22. The inner andpouter margins are preferably, but not necessarily continuous andcircular in shape. A fluid-impermeable barrier 26 having the shape of aring extends continuously on a lower surface portion of the sidewall 16and the compressed ring 18. The fluid-impermeable barrier 26 provides askin-facing surface 27 of the bandage 10 on which is disposed a ring ofadhesive material 28. The ring of adhesive material 28 may have arelease liner on its lower surface which is stripped away when thebandage 10 is to be attached to the skin of a patient. As best seen inFIG. 1A, the bandage 10 is attached to the skin of a patient by the ringof adhesive material 28 such that the sidewall 16 and the inner margin20 define an opening 23 that surrounds the bed of a wound 30 and a ringof peri-wound tissue 32 immediately adjacent to the wound 30. Above theopening 23, the space in the depression 14 forms a closed, dome-likestructure over the wound 30 which spans the wound 30 without contactingit. The enclosure 12, the sidewall 16, and the compressed ring 18 areformed integrally. Preferably, the integral structure is formed of amaterial that is light, flexible, yet of a nature that providesstructural integrity to the bandage 10, allowing it to stand uprightwhen attached as shown in the figures. As an example, the bandage 10 maybe formed by molding open cell foam material such as polyurethane. Thematerial is compressed to form the compressed ring 18 only for thepurpose of profiling the bandage 10. Such profiling is not a necessaryelement of the invention. Advantageously, the molded open cell foammaterial is also fluid absorbent. However the outer surface of themolded open cell foam material is treated to make it moistureimpermeable. In this regard, the outer surface of the bandage 10 may be“skunned” by mechanical or heat means that are well known in the art.Alternatively, a continuous film of moisture-impermeable material may beattached or laminated to the outside surface of the bandage 10. Theinside surface of the bandage 10, that is the surface of the molded opencell foam material that forms the depression 14, the lower surface ofthe sidewall 16, and the inner margin 20 is not treated in the manner ofthe outside surface of the bandage 10. In this regard, the insidesurface of the bandage over, about, and surrounding the wound 30 isfluid permeable, permitting exudate from the wound 30 to pass throughthe inside surface of the bandage 10 into the fluid absorbent materialof which the bandage 10 is formed. The barrier film layer 26 is fluidimpermeable for the purpose of preventing fluid which has been absorbedby the fluid absorbent material from moistening healthy skin underneaththe skin facing surface 27 and the ring of adhesive material 28. As analternative, the entire bottom surface of the sidewall could be madefluid impermeable, in which case the barrier film layer would beeliminated and the skin-facing surface 27 would be the b bottom surfaceof the sidewall 16. In this embodiment, the ring of adhesive material 28would be mounted directly to the bottom surface of the sidewall 16. Inoperation, the ring of adhesive material 28 is prepared for attachmentto the skin surface, and the bandage 10 is attached via the ring ofadhesive material 28 to the skin surface, positioned so that the innermargin 20 surrounds the wound 30, set back from the peri-wound area 32.As exudate is produced in the bed of the wound 30, it flows across theperi-wound area 32, contacting the fluid absorbent material at and nearthe inner margin, where it is absorbed into the bandage 10. At the sametime, fluid evaporates from the wound 30 and the skin, quickly raisingthe relative humidity within the enclosure to near 100%. The wound 30can not dry out in a 100% humid environment. Preferably, the bandage 10has a measurable moisture vapor transmission rate (MVTR), which isslight compared to the amount of fluid exuded from the wound 30.

[0048] The sealed enclosure formed by the bandage 10 has three purposes.First, it absorbs exudate produced at the wound 30, retaining most ifnot all of it in the molded open cell foam material through the insidesurface of the bandage 10. This eliminates pooling of exudate in thewound and promotes autolytic debridement. This also preventscontamination and the spread of pathogens and odors. Second, the bandage10 maintains an environment of high relative humidity over the wound 30.Finally, the sealed enclosure and its humid atmosphere effectivelythermally insulate the wound and peri-wound area from the ambientenvironment, which tends to maintain the temperature of wound andperi-wound area in a normothermic range of from about 36° C. to about38° C.

[0049]FIGS. 2 and 2A-2D illustrate a second embodiment of a bandage forautolytic debridement according to our invention. The bandage 210includes a sidewall 216 that has the shape of an torus, preferably acontinuous torus. A disk-shaped cover 215 is attached or bonded to oneside of the torus, over its center. The cover 215 and sidewall 216 forman enclosure having the shape of a doughnut with a cover on one side.The sidewall 216 has an inner surface 217 that transitions to a lip 218.The lip 218 projects inwardly into the opening of the torus formed bythe sidewall 216. The front edge of the lip 218 forms an inner margin220. The inner margin is preferably, but not necessarily, continuous andcircular in shape. The inner margin 220 defines an opening 223. A sidesurface of the torus formed by the sidewall 216 constitutes askin-facing surface 224. A ring of adhesive material 228 is disposed onthe skin-facing surface 224. The ring of adhesive material 228 may havea release liner on its lower surface which is stripped away when thebandage 210 is to be attached to the skin of the patient. As best seenin FIGS. 2A and 2B, the bandage 210 is attached to the skin of a patientby the ring of adhesive material 228 such that the sidewall 216 and theinner margin 220 define an opening 223 that surrounds the bed of a wound230 and a ring of peri-wound tissue 232 immediately adjacent the wound230. Above the opening 223, the space defined by the inner wall 217 ofthe sidewall 216 and the cover 215 forms a closed structure over thewound 230 which spans the wound 230 without contacting it. The cover 215and sidewall 216 are formed as separate single pieces. Preferably, thesidewall is formed of a material that is light, flexible, yet of naturethat provides structural integrity to the bandage 210, allowing it tostand upright when attached as shown in the figures. As with theenclosure of the first embodiment, the sidewall 216 may be formed bymolding open cell foam material such as polyurethane. The moldingprocess forms the sidewall 216 into the shape that includes the inwardfacing lip 218 that transitions to the inner margin 220. As with thefirst embodiment, the molded open cell foam material is fluid absorbent.However, the outer surface of the molded open cell foam material istreated to make it moisture impermeable as with the first embodiment.The cover 215 may comprise a thin sheet of flexible, transparent plasticmaterial that may be bonded by a continuous fluid-imperious seal, forexample, by adhesive, to the sidewall 216 in the manner shown in thefigures. For example, the cover 215 may comprise a 4 mil-thick sheet ofpolyethylene. The inside surface 217 of the bandage 210 is not treatedin the manner of the outside surface of the bandage 210. In this regard,the inside surface 217 is fluid permeable, permitting exudate from thewound 230 to be absorbed into the fluid-absorbent material of which thebandage 210 is formed. However, the fluid-impermeable treatment of theouter surface of the sidewall 216 extends to the skin-facing surface224, making that surface fluid-impermeable and preventing fluid whichhas been absorbed by the side wall 216 through the inner surface 217from moistening healthy skin underneath the skin-facing surface 224 andthe ring of adhesive 228. In operation, the ring of adhesive material228 is prepared for attachment to the skin surface, and the bandage 210is attached via the ring of adhesive material 228 to the skin surface,positioned so that the inner margin 220 surrounds the wound 230, setback from the peri-wound area 232. As exudate is produced in the bed ofthe wound 230, it flows across the peri-wound area 232, contacting thefluid absorbent material at, near, and above the inner margin 220 alongthe surface 217, where it is absorbed into the bandage 210. At the sametime, fluid evaporates from the wound 230 and the skin, increasing therelative humidity within the enclosure formed by the cover 215 and thesidewall 216 to near 100%. This prevents the wound 230 from drying out.Preferably, the MVTR through the bandage 210 is slight compared to theamount of fluid exuded from the wound 230. The lip 218 provides contourthat promotes the flow of fluid exuded from the wound 230 upward alongthe surface 217. Thus, if the bandage 210 is disposed so as not to beabsolutely horizontal, fluid from the wound 230 will tend to flow alongthe upward curve of the lip 218 along the surface 217 to be absorbedthrough that surface into the fluid absorbent material of which thesidewall 216 is formed. In the second embodiment of our bandage forautolytic debridement, the inner margin 220 may be provided on contoursother than the curved lip 218 of FIGS. 2A and 2B. For example, in FIG.2C, the sidewall 216 may be shaped to provide an inner surface 217 athat is rounded outwardly of the torus shape so that the inner margin220 a is provided where the fluid permeable inner surface 217 atransitions to the fluid-impermeable skin-facing surface 224. In FIG.2D, the sidewall 216 is shaped with a straight, flat inner surface 217 bthat is fluid permeable. In this case, the inner margin 220 b isprovided along the bottom edge of the inner surface 217 b.

[0050]FIGS. 3 and 3A illustrate a third embodiment of a bandage forautolytic debridement according to our invention. The bandage 310 has asidewall 316 in the form of a pouch having the overall shape of squareor rectangular annulus. As best seen if FIG. 3A, the pouch of which thesidewall 316 is comprised has a generally rectangular cross-section withrounded ends 316 a and 316 b. Being a pouch, sidewall 316 has aninterior space. A cover 315 is attached to an upper surface 321 of thesidewall 316, continuously around the sidewall 316 to form an enclosuretherewith. The sidewall 316 has an inner side surface 317 and thesurface 321 has an interior surface portion 321 a. Holes 319 areprovided through the inner surface portion 321 a and the inner surface317. The holes (or apertures or ports) open into the interior space ofthe pouch of which the sidewall 316 is comprised. An inner margin 320,which is preferably but not necessarily continuous, defines an opening323. The interior space of the pouch of which the sidewall 316 iscomprised is filled with a fluid-absorbent material 325. The bottom ofthe sidewall 316 has a skin-facing surface 327 that is unapertured. Asquare or rectangular annulus of adhesive material 328 is disposed onthis skin-facing surfacing 327. The adhesive material 328 may have arelease liner on its lower surface which is stripped away when thebandage 310 is to be attached to the skin of a patient. As best seen inFIG. 3, the bandage 310 is attached to the skin of a patient by the ringof adhesive 328 such that the sidewall 316 and the inner margin 320define the opening 323, with the opening 323 surrounding the bed of awound 330 and ring of peri-wound tissue 332. Above the opening 323, thecover 315 exhibits an upwardly rising, dome-like structure that risesabove the inner surface portion 321 a in order not to occlude the holes319 in that inner surface portion. As FIG. 3 shows, the cover 315 andsidewall 316 form an enclosure over the wound 330 which spans the wound330 without contacting it. Preferably, the cover 315 is formed of asturdy, yet somewhat flexible, moisture-impermeable, desirably (but notnecessarily) transparent material. The material should be sturdy enoughto form and maintain the dome that rises over the opening 323.Flexibility is necessary to accommodate various contours that areencountered on the surface of a body. For example, the cover 315 maycomprise a 4 mil-thick sheet of molded polystyrene or polyester orpolyvinylchloride or equivalent material that is attached or bonded by acontinuous, closed seam acting between the surface 321 of the sidewall316 in the outer periphery of the cover 315. The bond that joins thecover 315 with the sidewall 316 may be a permanent bond, or an adhesiveseam that permits the cover 315 to be removed from the sidewall 316. Thesidewall 316 may be formed of the same material as the cover 315. Whenfilled with the fluid-absorbent material 325, the sidewall 316 providesa light, flexible structure that affords structural integrity to thebandage 310, allowing it to stand upright when attached as shown in thefigures. The fluid-absorbent material 325 that fills the interior of thesidewall 316 may comprise, for example, an alginate. The inside surface317 and the inner surface portion 321 a, both of which are apertured,provide ingress to fluid, permitting exudate from the wound 330 to flowinto the interior space of the sidewall 316 there to be absorbed andretained by the fluid absorbent material 325. Since the surfaces 321 and327 are unapertured, fluid that is absorbed by the fluid-absorbentmaterial 325 is prevented from moistening healthy skin underneath theskin-facing surface 327 and the ring of adhesive 328. In operation, thering of adhesive 328 is prepared for attachment to the skin surface, andbandage 310 is attached via the ring of adhesive 328 to the skinsurface, positioned so that the inner margin 320 surrounds the wound330, set back from the peri-wound area 332. As exudate is produced inthe bed of the wound 330, it flows across the peri-wound area 332,contacting the inner surface 317 and the inner surface portion 321 a,flowing through the apertures 319 into the interior of the sidewall 316where it is absorbed by the fluid absorbent material 325. At the sametime, fluid evaporates from the wound 330 and the skin, raising therelative humidity within the enclosure to near 100%, thereby preventingdrying of the wound 330. Preferably, the material of which the cover 315and sidewall 316 are formed provides a measurable MVTR, which is slightcompared to the amount of fluid exuded from the wound 330.

[0051] Referring now to FIGS. 4 and 4A, a fourth embodiment of thebandage for autolytic debridement according to our invention isillustrated. The bandage 410 includes a cover 412 that is circularlyshaped and molded to form an enclosure with a flattened dome. At itsmargin, the cover 412 transitions to a lip 413, on the bottom of whichis a first skin-facing surface 414. A sidewall 416 has the shape of anannulus, preferably a continuous annulus that includes an inner ring ofmaterial 417 and an outer ring of material 419. The bottom surface ofthe inner ring of material 417 is a second skin facing surface 418. Aninner margin 420 defines an inner circumference of the inner ring ofmaterial 417. An inner surface 421 rises from the inner margin 420. Thesidewall 416 and the inner margin 420 define an opening 423. One or moregrooves 425 extend radially on the upper surface of the sidewall 416extending from the top of the inner surface 421 to the outer peripheryof the sidewall 416, traversing both the inner and outer rings ofmaterial 417 and 419. A ring of adhesive material 428 is disposed on thefirst skin-facing surface 414. The ring of adhesive material 428 mayhave a release liner on its lower surface which is stripped away whenthe bandage 410 is to be attached to the skin of the patient. As seen inthe figures, the bandage 410 is attached to the skin of a patient by thering of adhesive material 428 such that the opening 423 defined by thesidewall 416 and the inner margin 420 surrounds the bed of a wound 430and a ring of peri-wound tissue 432 immediately adjacent to the wound430. Above the opening 423, a closed space is defined over the wound 430by the sidewall 416 and the cover 412. The cover 412 and sidewall 416may be formed as separate single pieces. Preferably, the sidewall isformed of two materials, both light, flexible, yet of a nature thatprovides structural integrity to support the cover 412 upright over thewound 430 when attached as shown in the figures. The sidewall 416 ispreferably a single integral piece that unifies the inner ring ofmaterial 417 and the outer ring of material 419. The inner ring ofmaterial 417 is, preferably, a fluid absorbent material such as a moldedopen cell foam. Preferably the second skin-facing surface 418 is treatedso as to be fluid impermeable. However the inner surface 421 and theupper surface of the inner ring of material 417 are fluid permeable. Theouter ring of material 419 is preferably a fluid impermeable materialsuch as molded closed cell foam. Alternatively, the inner and outerrings of material 417 and 419 may both be fluid absorbent, yet exhibitdifferent degrees of absorbency. For example, the inner ring of material417 may comprise a very open porous material into which thick, viscousexudate is readily absorbed. In this case, the outer ring of material219 may comprise a somewhat less open material into which thinner, lessviscous exudate is received. The inner and outer rings of material 417and 419 may be molded separately and bonded together or formed in amulti-step molding process. The cover 412 may comprise a thin moldedsheet of flexible, transparent plastic material that may be bonded by acontinuous fluid-impervious seal (for example adhesive) to the sidewall416 in the manner shown in the figures. The bond that joins the cover412 with the sidewall 416 may be a permanent bond, or an adhesive seamthe permits the cover 412 to be removed from the sidewall 416. Forexample, the cover 415 may comprise a molded 4 mil-thick sheet ofpolyethylene or equivalent material. Since the inside surface 421 of thesidewall 416 is fluid permeable, it permits exudate from the wound 430to be absorbed into the fluid-absorbent material of the inner ring ofmaterial 417. However, the fluid-impermeable treatment of the secondskin-facing surface 418 and the fluid-impermeable material of the outerring of material 419 prevent fluid which has been absorbed into theinner ring of material 417 from moistening healthy skin underneath oroutside of the second skin-facing surface 418. In operation, the ring ofadhesive material 428 is prepared for attachment to the skin surface,and the bandage 410 is attached via the ring of adhesive material 428 tothe skin surface, positioned so that the inner margin 420 surrounds thewound 430, set back from the peri-wound area 432. As exudate is producedin the bed of the wound 430, it flows across the peri-wound area 432,contacting the molded open cell foam material of the inner ring ofmaterial 417 at, near, and above the inner margin 420 along the surface421, where it is absorbed into the bandage 410. At the same time, fluidevaporates from the wound 430 and the skin, increasing the relativehumidity within the enclosure formed by the cover 412 and the sidewall416 to near 100%. This prevents the wound 430 from drying out.Preferably, the MVTR through the bandage 410 is slight compared to theamount of fluid exuded from the wound 430. The grooves 425 providechannels that promote the flow of fluid exuded from the wound 430 alongthe upper surface of the sidewall 416. Thus, if the bandage 410 isdisposed so as to not to be absolutely horizontal, fluid from the wound430 may flow along one or more of the grooves 425 to be absorbed intothe material of the inner ring of material 417.

[0052]FIGS. 5 and 5A illustrate a fifth embodiment of a bandage forautolytic debridement according to our invention. The bandage 510includes a cover 512 identical to the cover 412 of the fourth embodimentillustrated in FIGS. 4 and 4A. In this regard the cover 512 is a molded,circularly-shaped piece that has a lip 513 and first skin-facing surface514. The sidewall 516 of the fifth embodiment bandage includes a flatcircular container 517 having a circumferential outer rim 518 that risesabove a floor 519. A second skin-facing surface 520 is on the bottom ofthe flat circular container 517. An inner margin 522 defines an opening523 through the floor 519 of the flat circular container 517. Concentricrings of material 524 a and 524 b are disposed within the flat circularcontainer 517. The diameter of the first ring of material 524 a is lessthan the diameter of the second ring of material 524 b; both rings ofmaterial are substantially centered in and concentric with the outer rim518 of the flat circular container 517. Preferably, the elements of thesidewall 516, including the flat circular container 517, the first ringof material 524 a, and second ring of material 524 b, are all fluidabsorbent, preferably made of a molded open cell foam material. However,at least the second skin-facing surface 520 of the flat circularcontainer 517 is treated as described above with reference to the firstembodiment so as to be fluid impermeable. All surfaces of the first andsecond rings of material 524 a and 524 b and the interior surface of theflat circular container 517 are not treated and are therefore fluidpermeable, enabling the flow of exudate through those surfaces into thematerial of which their respective structures are formed. Preferably,the flat circular container 517, the first ring of material 524 a andthe second ring of material 524 b are an integral piece, either formedin the same or successive steps, or formed separately and bondedtogether. Concentric channels 526 and 527 are formed between the firstring of material 524 a and the second ring of material 524 b, andbetween the second ring of material 524 b and the outer rim 518 of theflat circular container. In addition, radial channels are formed bynotches 529 formed in the first and second rings of material 524 a and524 b that are aligned along a radius of the flat circular container517. A ring of adhesive material 528 is mounted on the first skin-facingsurface 514 on the cover 512. The ring of adhesive material 528 may havea release liner on its lower surface which is stripped away when thebandage 510 is to be attached to the skin of the patient. As the figuresshow, the bandage 510 is attached to the skin of a patient by the ringof adhesive material 528 such that the opening 523 defined by the innermargin 522 surrounds the bed of a wound 530 and a ring of peri-woundtissue 532 immediately adjacent the wound 530. Above the opening 523,the space defined between the cover 512 and the sidewall 516 forms aclosed structure over the wound 530 which spans the wound 530 withoutcontacting it. The cover 512 and sidewall 516 are separate, singlepieces. Preferably the sidewall 516 is formed as described above,comprising a material that is light, flexible, yet of a nature thatprovides structural integrity to the bandage 510 and support to thecover 512, allowing the bandage 510 to stand up right when attached asshown in the figures. The cover 512 may comprise the material of, and beformed as described above in connection with, the fourth embodiment. Thecover 512 may be bonded by a continuous fluid-impervious seal to thesidewall 516 in the manner shown in the figures. The bond that joins thecover 512 with the sidewall 516 may be a permanent bond, or an adhesiveseam that permits the cover 512 to be removed from the sidewall 516.Since the inside surfaces of the flat circular container 517 and allsurfaces of the first and second rings 524 a and 524 b are fluidpermeable, exudate from the wound 530 is permitted to be absorbed intothe fluid absorbent material of which the flat circular container 517and the rings 524 a and 524 b are formed. However, the fluid-impermeabletreatment of the second skin-facing surface 520 makes that surfacefluid-impermeable, thereby preventing fluid which has been absorbed intothe sidewall 516 from moistening healthy skin underneath the skin-facingsurface 520. In operation, the ring of adhesive material 528 is preparedfor attachment to the skin surface, and the bandage 510 is attached viathe ring of adhesive material 528 to the skin surface, positioned sothat the inner margin 520 surrounds the wound 530, set back from theperi-wound area 532. As exudate is produced in the bed of the wound 530,it flows across the peri-wound area 532, contacting the fluid absorbentmaterial of the first and second rings of material 524 a and 524 b. Inaddition, the radial channels formed by the notches 529 provide ingressto the exudate fluid into the concentric channels 526 and 527. Theconcentric channels 526 and 527 conduct and distribute the fluid overthe sidewalls of the rings of material 524 a and 524 b, the floor 519 ofthe flat circular container 517 and the inner wall of the outer rim 518.All of these surfaces are fluid permeable and provide a path into thefluid absorbent material of which their respective structures areformed. Reference is made to a first circular tear line 525 a in thechannel 526 between the first and second rings of material 524 a and 524b and a second tear line 525 b in the channel 527 between the secondring of material 524 b and the outer rim 518. These lines of weaknesspermit the flat circular container 517 to be modified by removal ofannular sections of the sidewall 516. For example, the portion of thesidewall between the first tear line 525 a and the inner margin 522 maybe separated entirely from and removed from the bandage 510. Thisprovides an opening 523 having a larger diameter then that shown in FIG.5 and moves the inner margin 522 diametrically toward the outer rim 518.These tear lines permit the bandage 510 to be configured to accommodatewounds of varying sizes.

[0053]FIGS. 6 and 6A illustrate a sixth embodiment of a bandage forautolytic debridement according to our invention. The bandage 610 isidentical in all respects with the bandage 510 illustrated in FIGS. 5and 5A. In addition, circular members 650 are disposed within thesidewall 616, concentrically interspersed with the first ring ofmaterial 624 a, the second ring of material 624 b, and the outer rim 618of the sidewall 616. Each of the circular members 650 comprises a fluidabsorbent material such as an alginate, hydrogel, or hydrocolloid.Alternatively, the circular members 650 can comprise a wicking material.In either case (or in both cases if both types of materials are used),the circular members 650 promote the transport and absorption of exudatefluid from the wound 630 and the peri-wound area 632 to and into thefluid absorbing members of the sidewall 618.

[0054]FIGS. 7 and 7A illustrate a seventh embodiment of a bandage forautolytic debridement according to our invention. The bandage 710includes a sidewall 716 that is identical in all respects with thesidewall 316 of the third embodiment illustrated in FIGS. 3 and 3A, withone exception. That exception is that the entire surface of the sidewall716 is apertured by holes 719 that permit exudate to enter the sidewallthe 716, there to be absorbed by fluid-absorbent material 725. A cover715 identical in all respects with the cover 315 of the third embodimentbandage 310 is sealingly bonded to the sidewall 716. An additionalshaped or molded plastic member 750 in the shape of a square orrectangular annulus or skirt is bonded near a first edge 751 to an uppersurface of the cover 715 along the periphery of the cover 715 by acontinuous, fluid-impervious seal. The plastic member 750 is shaped totransition to a lip 752, a bottom surface of which forms a skin-facingsurface 753 on which is mounted a ring of adhesive material 728. Thestructure, materials and operation of the bandage 710 are as describedabove for the bandage 310. Preferably, the plastic member 750 is moreflexible than the cover 715, not needing the dome-supporting ability ofthat element.

[0055] Manifestly, each of the seven embodiments illustrated in thefigures and discussed in the specification forms a sealed enclosure thatsatisfies the three purposes set forth above for the first embodiment.That is, each embodiment absorbs exudate produced at a wound, retainingmost of if not all of the exudate in fluid-absorbent material that isbrought into the structure of the bandage at least on an inside surfacethat is near a margin defining an opening about a wound. This eliminatespooling of exudate in the wound and promotes autolytic debridement. Thisstructure also prevents contamination and the spread of pathogens andodors. Second, each embodiment of the bandage maintains an environmentof high relative humidity over a wound. Finally, each embodimentprovides a sealed enclosure which, together with the humid atmospherewithin the enclosure, effectively thermally insulates a wound andperi-wound area from an ambient environment, which tends to maintain thetemperature of the wound and peri-wound area in a normothermic range offrom about 36° C. to about 38° C.

[0056] In the description of our invention, we have disclosed certainstructural members of a bandage for autolytic debridement as comprisingfluid-absorbent material. One specific instantiation of such materialhas been disclosed: molded open-cell foam. This is not intended to limitthe practice of our invention to the use of that specific material.Instead, any material that can provide the necessary structural featuresis contemplated, so long as one or more surfaces of a member made of thematerial can be made fluid-impermeable without limitation. Other fluidabsorbent materials may include hydrogels and hydrocolloids, forexample.

[0057] Other features may be incorporated into our invention. Forexample, in any of the embodiments shown, the fluid absorbing materialmay be impregnated with hydrophilic material to increase itsfluid-storing capacity, with odor-absorbing material, such as charcoal,and/or with treatment material such as antibiotics or medicants.

[0058] Moreover, features, functions and/or structures described for oneembodiment may be incorporated into one or more of the otherembodiments. For example, the ability to detach rings in the fifth andsixth embodiments may be incorporated in the fourth. Variability in thefluid absorption characteristics of different members that was describedin connection with the fourth embodiment could be incorporated into atleast the fifth and sixth, if not all of the remaining embodiments.

[0059] This description may have described features, elements, andlimitations of our invention in the singular. This is not meant to solimit the implementation of our invention in any case where the pluralcould be used.

[0060] It should be clear that our invention comprehends a method fortreating a wound by promoting autolytic debridement. In this regard, awound treatment apparatus (or “bandage” or “plaster”) having a fluidimpermeable enclosure with a sidewall forming a margin that defines anopening is provided, the wound treatment apparatus including a fluidabsorbent material disposed in the enclosure. The fluid absorbentmaterial is disposed at, or near the margin, out of the opening. Thewound treatment device also includes an attachment device (or a meansfor attachment) on a skin-facing surface of the enclosure. The enclosureis brought against the surface of a human (or animal) body such that theattachment device attaches the wound treatment device to the surface ata location that creates a closed, substantially fluid impermeableenvironment over a wound, with the wound in the opening, substantiallyencircled by the margin. The closed, substantially, fluid impermeableenvironment creates a humid atmosphere within the enclosure, about thewound that maintains a temperature about the wound at or near anormothermic level in the range of about 36° C. to about 38° C. Fluidexudate produced in or near the wound is collected and held in the fluidabsorbent material as the wound heals.

[0061] While our invention has been illustrated and described withreference to particular embodiments, it will be understood by thoseskilled in the art that various changes and modifications can be made tothose embodiments, and other embodiments can be provided, withoutdeparting from the scope of the invention, which is limited only by thefollowing claims.

We claim:
 1. A bandage for autolytic debridement, comprising: anenclosure having a fluid-impermeable outer surface, a sidewall thatforms a margin defining an opening, and a skin-facing surfacesurrounding the opening; an attachment means disposed on the skin-facingsurface for attaching the enclosure to skin such that the enclosurecreates a closed, fluid-impermeable chamber over a wound, substantiallywithout contacting the wound; and a fluid absorbent material disposedwithin the enclosure substantially near the margin and out of theopening.
 2. The bandage of claim 1, wherein the sidewall forms asubstantially annular base.
 3. The bandage of claim 1, wherein thesidewall forms a torus.
 4. The bandage of claim 1, wherein the enclosureis formed of the fluid absorbent material.
 5. The bandage of claim 1,wherein the sidewall is formed of the fluid absorbent material.
 6. Thebandage of claim 1, wherein the sidewall contains the fluid absorbentmaterial.
 7. The bandage of claim 1, further including one or morewicking members in contact with the fluid absorbent material.
 8. Thebandage of claim 1, wherein the sidewall containing the fluid absorbentmaterial, the bandage further including apertures in the pouch.
 9. Thebandage of claim 1, further comprising one or more wicking members, thebandage further including means acting between the sidewall and the oneor more wicking members for supporting the one or more wicking members.10. The bandage of claim 7, further including means for conducting fluidfrom the opening to the one or more wicking members.
 11. The bandage ofclaim 1, wherein the enclosure further includes a cover that spans thesidewall, the cover including the skin-facing surface.
 12. The bandageof claim 11, wherein the cover is formed of a fluid-impermeablematerial.
 13. The bandage of claim 1, wherein the sidewall includes atleast two members.
 14. The bandage of claim 13, wherein the at least twomembers include two concentric members.
 15. The bandage of claim 13,wherein a first member includes the fluid absorbent material and asecond member includes a non-fluid absorbent material.
 16. The bandageof claim 13, wherein a first member includes a first fluid absorbentmaterial and a second member includes a fluid absorbent material.
 17. Amethod for treating a wound by promoting autolytic debridement with awound treatment device that includes a fluid impermeable enclosure witha sidewall that forms a margin defining an opening, a fluid absorbentmaterial in the enclosure, near the margin, out of the opening, and ameans for attachment to a skin surface, comprising: placing theenclosure at a location over a wound with the wound substantially in theopening, surrounded by the margin; attaching the enclosure to the skinto form a substantially fluid-impermeable enclosure over the wound; andcollecting fluid produced by the wound in the fluid absorbent material,out of the opening and away from the wound.
 18. The method of claim 17,wherein attaching the enclosure creates a humid atmosphere about thewound, within the enclosure.
 19. The method of claim 17, whereinattaching includes maintaining a humid atmosphere about the wound,within the enclosure.
 20. The method of claim 19, wherein attaching andmaintaining a humid atmosphere further include maintaining a temperatureabout the wound, within the enclosure in the range of about 36° C. toabout 38° C.
 21. A method for treating a wound comprising: placing afluid-impermeable enclosure over and about a wound; maintaining anatmosphere within the enclosure which is humid and at a normothermictemperature; and collecting fluid produced by the wound within theenclosure, away from the wound.